We begin the day like we usually do: competing. We push ourselves, sprinting away from Vance’s home, standing on the pedals to race up the first few hills, breaking a quick sweat. But here’s the thing: That kind of riding makes no sense in San Francisco. The city, with its heavy traffic and its stoplights, is designed for stop-and-go riding, not go and go. The same is true of our bikes. The loaner I’m ­pedaling is an eight-speed cruiser of indeterminate brand that feels as heavy as a moped and is notable mainly for the chunky metal basket over the front wheel. It’s missing only a bouquet of daisies and a much prettier rider to complete the look it seems to be going for. Vance is on a swankier bike, a Moots Comooter, the priceyness of which, in practice, detracts from its utility, since locking it up to anything short of an armed guard would make me anxious.

But by lunchtime we’re no longer racing. Instead, we’re cruising slowly through the Mission District, pretty much drowning in slow-pour coffee shops, when Vance announces we’re only a block from one of his favorite taco joints. Soon our bikes are locked up and we’re lounging on a sunny little side patio. By our third bowl of chips I’m agonizing over whether to have a second margarita ­picante. It features a base of el Jimador tequila, a generous squeeze of lime, and a dash of red-chili-pepper-infused vinegar. Goes down perfect with pork-belly tacos. Vance catches my eye and smirks.

“Tough gig,” he says. Vance is one of my best friends. We’ve plunged into all sorts of adventures for a dozen years now, most of them involving physical or psychological extremes. We’ve gotten lost kayaking in Louisiana’s Atchafalaya Swamp, run out of water while hiking in the Navajo Nation, and braved an amateur porn shoot in downtown Atlanta. (Long story, that one.) We tend to do things that push both of us to the limits of our comfort zones.

And then there’s today. How did we end up on this, a languid two-wheeled excursion to the intersection of Sloth and Gluttony? Pretty simple: Vance lives here, and I’m passing through town. We needed time to catch up, and hanging around his house in Noe ­Valley was out of the question because Vance’s wife just had a baby. We had the idea to ride, not in any serious way, but in the way people ride now across weekends like this one in cities all over North America: on sturdy, upright, gracefully plain bikes, in no hurry and with no significant agenda, in meaningful pursuit of meaningless fun. Two bikes, two friends, one city.

San Francisco is an empty slate for both of us, cycling-wise. Vance has done an Ironman on his Cervélo and is obsessive about his gearing and wattage, but he does most of his rides on the long open roads north of the city. Me, I hardly know the city, but I’m thinking of moving to the West Coast and am eager to explore.

As a further disincentive to ride hard, there are all the distractions we’re finding along the way, distractions that seem ­determined to make mincemeat of any mettle-testing gauntlet we might want to throw down. Distractions like these margaritas.

As we lounge, Vance brings up the last time we ate at a Mexican restaurant. It was a little over a year ago, and we were in Tecate, Mexico. We’d spent the previous several days hiking along the ­border. We drank tequila and ate grilled nopal cactus, then camped in a shallow gully 18 miles out of town, a spot notorious for its drug smuggling and bandits. Vance slept with one eye open and a machete under his pillow. I had a can of bear spray in my sleeping bag.

And you know what? That was fun, in its own adrenalized way. But we’re finding now that not all merriment needs an edge to it. We toast to the mild Northern California sunshine, finish the drinks—one’s enough for now—and head back outside to our bikes.

We have no route. We wander. Our stop-and-go pacing becomes stop and stop. A few minutes past the taco place, a patchwork of bright colors draws us into a narrow alleyway, and we find ourselves pedaling slowly past dozens of gorgeous murals that cover the brick and concrete walls on both sides, creating the sensation of gliding through a sort of urban coral reef.

From there it’s only a couple of easy and, for San Francisco, relatively flat miles to downtown. We dismount in a crowded square for a while to watch some street performers, including a disheveled dance troupe, a somewhat ornery one-man band—“usually people clap when I do that,” he says after getting a lackluster response to his foot-driven drum solo—and a sharp-dressed older gentleman railing against recreational procreation. Although San Francisco has a deserved reputation for being bike-friendly, the downtown area, with its combination of wheel-catching recessed trolley tracks and bike lanes that plop you uncomfortably between car and bus traffic, is still the kind of place where you have to keep sharp. Skipping that second margarita turns out to be a wise move.

After looping around through the Tenderloin District and back through the Mission, we eventually find ourselves pedaling through the heart of the Castro, where I spot two emphatically naked men loitering near a disinterested policeman. A quick Google query confirms that public nudity is in fact legal in this city. After a few easy rises, we crest a hill and begin a long descent, speeding through a gate marking an entrance to the Presidio and plummeting down through a sparse grove of redwoods toward the bay.

“Want to stop by George Lucas’s place?” Vance shouts back.

My name is Luke. I was born in the ’70s. Of course I do.

The headquarters of Lucas’s empire occupies a sprawling complex maybe a quarter-mile inland, and we weave through it on wide ribbons of pavement, stopping to read the plaques by the statues that Lucas has erected in honor of other San Franciscan pioneers of the moving-picture arts. I stop and tap a note into my phone: The inventor of the television is named Philo Farnsworth! How is it I’ve never heard of him? A little later I notice a wizened old couple sitting on a bench near a fountain topped by a Yoda statue.

We also cover lots of other kinds of ground. Usually, when Vance and I are hanging out, we’re so consumed by the task at hand that we end up limiting communication to the bare essentials: food, water, direction, pace. One of the advantages of not pushing high rpms or high anxiety today is that we actually have a chance to, well, talk. Our conversation roams as free and wide as our ride.

Vance is a new father, has a two-week-old boy who spends his days lazing and howling, incontinent and inchoate. I’ve got a five-year-old daughter, and I remember those first strange days, the fear and the wonder and the exhaustion. I also remember how Vance gave me shit back then. Whenever I’d talk about something like the relative merits and price points of jogging strollers, he’d react with a sort of disgusted horror, tell me I might as well have been debating various brands of denture cleansers. Now, meandering around Lucas’s dream factory, I take some satisfaction in listening to Vance ramble about Baby Bjorns and breast pumps.

We stop in for more drinks and food at the Presidio Social Club, a restaurant ensconced in a century-old military barracks. Cocktails and pork belly redux. There’s a group of people dressed in vintage 1930s military uniforms eating at the bar, and they tell us they’re on their way to a Great Gatsby-themed costume party elsewhere in the city. They invite us to come along, and it’s tempting, but what I really want to see is the water.

It’s an easy coast down from the restaurant to Crissy Field, where we join the herd of other pleasure cruisers pedaling parallel to the bay. There are little kids with kites on the field, and big kids with kiteboards on the water. This whole area used to be an Air Force installation, and I notice that one of the old hangars has its huge doors flung open. Inside, I catch a glimpse of people flying. Further investigation reveals that the hangar has been converted into something every city should have: a trampoline gym. We dock the bikes, sign some waivers, purchase some sticky-bottomed purpose-built socks, and spend an hour enjoying another simple invention that instantly endows you with superhuman powers.

By the time we’re back outside, the sun has started to arc down behind the Golden Gate Bridge, backlighting it, making it live up to its name. We head east along the marina for a while, slowly enough to discuss in detail where we might go next, literally and metaphorically. Vance has decided to buy himself a second bike, something to ride around town on, something cheap and easy and reliable. He’s also thinking that maybe a baby trailer could be fun. Me? Well, if I can find an apartment that rents for less than the price of a Cervélo, I’m sold on San Francisco. It’s been that kind of day. But the wind is kicking up now, and it’s getting cold. Time to head back to Vance’s place. At this point, we’ve got two options. The first is a long and winding but relatively gradual ascent back toward Noe Valley. The second way, on Divisadero, is very direct and very steep.

There’s nothing wrong with taking it easy, and a lot right. But an outing with Vance just wouldn’t feel complete without at least a little pain. We turn our bikes onto Divisadero, point them uphill, and begin what will be, after a bit too much pork belly, a long and exceedingly harsh climb.